This invention relates to train wheel wear measurement gauges and instruments and more particularly, to a wheel wear measurement system which is small, portable and capable of providing repeatability to all critical wheel wear measurement readings irrespective of the operator.
Train wheels are subject to normal wear due to friction contact between the wheel and the rail. As the train wheels wear out, the rim thickness and flange thickness decrease and the flange height increases. There is a need to accurately measure the rim thickness, flange thickness, and flange height in order to ensure that the wheels in operation have enough metal on them. These safety check measurements take place in train yards and in train shops. Similar measurements are used in recutting (wheel truing) the wheels to restore wheel profile as the wheel wear exceeds certain permissible tolerances of flange height, and flange thickness. The wheel truing operation takes place in train shops. Also, similar measurements are used by the wheel manufacturers for production quality control of train wheels.
Historically, these measurements have been taken using mechanical calipers. One such widely used mechanical wheel gauge looks like an inverted "J". In use, the readings are read and recorded by the operator directly off the mechanical gauge while it is placed on a wheel. There are several drawbacks, however, to such a mechanical gauge in all of the above mentioned applications. In an installed train wheel situation, for example, there are two major problems. First, the train wheel has quite a few mechanical parts such as brakes, shock absorbers and axle support mechanism around it. These measurements have accordingly been extremely difficult to take with the mechanical gauge because of the limited space around the wheel and location of a flange on a train wheel (towards the inside of a track). Second, the poor ambient conditions where the measurements are made, such as dim light make this task extremely difficult to perform. Further, operator dependent manual recording errors of these measurements, and keypunch errors, make this important wheel wear monitoring process on installed wheels very undependable. Measurement error can lead to three problems for the railroad. First, unacceptable wheels can remain in service providing an uncomfortable ride and posing a significant safety and liability hazard; second, wheels can be condemned which should be trued; and third, wheels which should be condemned are sometimes sent for truing, resulting in a disruption of the work flow in the wheel truing shop.
The mechanical gauge has been in use since 1923. Nevertheless, every year a number of train accidents are attributed to excessively worn out wheels. Inattention to excessively worn out wheels by train maintenance staff due to measurement errors, contributes to this safety risk. Several train companies have invested heavily in computerized wheel management systems which are designed to automate the wheel maintenance process. However, the current mechanical gauge does not provide accurate measurements to feed the computerized wheel management systems. Furthermore, the wheel maintenance staff cannot restore a wheel to the prescribed profile when they are unable to take accurate wheel wear measurements.
Several attempts have been made to automate the wheel wear measurement process. One arrangement is featured in a published U.K. Patent application No. GB 2183840A (published June 10, 1987, Martti Kurkinan, inventor). This arrangement measures only rim profile using an electro-mechanical contact probe which travels across the rim. Measured profile is compared with a good reference profile gathered using a second probe. Another arrangement is mentioned in a European patent application, publication No. EP 0007227A1 (W. H. Steel, et al., inventors). This arrangement suggests using a high intensity light source and a TV camera to gather information about surface profile. There are several problems with these rim profile measurement arrangements such as non-portability, inability to gather other vital measurements, and significant mechanical wear of the instrument.
Therefore, there presently exists a genuine need for a portable electronic train wheel gauge capable of improving the integrity of the wheel wear measurement process by facilitating accurate and repeatable wheel wear measurements, ensuring proper gauge head alignment with respect to the wheel, reducing the opportunities for operator errors, and by directly feeding the maintenance computer.